The black-legged tick, Ixodes scapularis Say, is the vector of at least three tick-borne diseases in the northeastern and Midwestern US: human granulocytic anaplasmosis, babesiosis, and Lyme disease, the most important vector-borne illness in the country. Efforts to reduce the incidence of these diseases must encompass strategies to reduce vector populations. Long-term life history data for I. scapularis indicate that natural regulatory processes are in place that routinely account for cumulative larval to adult mortality rates in excess of 95%. These processes have remained largely unidentified but the ubiquity of entomopathogenic fungi at the soil surface, where I. scapularis spends most of its two-year lifespan, and promising lab results demonstrating the acaricidal properties of such fungi, suggest they may be a significant source of mortality in situ. A biocontrol strategy that augments natural mortality at each stage of the tick's life cycle would be a significant advance over current practices that are either inefficient or have negative impacts on the environment. The primary goals of the proposed study are to identify entomopathogenic fungi that exist in woodland habitats where ticks are found, to quantify infection rates in ticks, and determine what seasonal patterns and habitat features are associated with fungus presence. The combination of methods we will employ using culture, bait organisms to "trap" entomopathogenic fungi, and DNA extraction will represent the most comprehensive attempt to identify and quantify entomopathogenic fungi in nature. Once the variety of entomopathogenic fungi affecting ticks is documented, virulence assayed, and the seasonal patterns of abundance that may indicate differential impacts on particular life stages demonstrated, the potential exists to develop effective biocontrol strategies that augment natural regulatory mechanisms. Our ability to extract fungal DNA from soil and tick samples, along with our ongoing work to design appropriate primers to detect fungi, has already revealed that entomopathogenic fungi more frequently infect I. scapularis than previously thought. Furthermore, this will be the first study to document the seasonal distribution of entomopathogenic fungal species in the northeastern US. By investigating the role of these fungi in regulating I. scapularis and understanding the ecology of these organisms, we anticipate development of natural ways to impose further controls on tick populations and the spread of disease. Current tick control strategies are either inefficient or harmful to the environment. A biocontrol strategy that takes advantage of regulatory mechanisms already existing in nature could have a profound impact on public health by targeting the most susceptible tick stage(s), at the appropriate time, without imposing negative environmental impacts. This project will determine if entomopathogenic fungi can serve as the foundation for such a biocontrol strategy. These fungi show promise in terms of their distribution in the environment and virulence to I. scapularis in lab studies. Long- term health benefits might also accrue with the reduction in pesticide use those results from the availability of an effective biocontrol agent. [unreadable] [unreadable] [unreadable] [unreadable]